Linux KernelOperating system · Linux
CVE-2021-3714
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA flaw was found in the Linux kernels memory deduplication mechanism. Previous work has shown that memory deduplication can be attacked via a local exploitation mechanism. The same technique can be used if an attacker can upload page sized files and detect the change in access time from a networked service to determine if the page has been merged.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceA flaw in the Linux kernel's memory deduplication (KSM) mechanism allows a local attacker to determine if specific memory pages have been merged by uploading page-sized files and measuring access time changes through a networked service. This is a side-channel attack exploiting the timing difference when memory pages are merged.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Linux KernelOperating system
all versions
Enterprise LinuxOperating system
= 6.0= 7.0= 8.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check if KSM is enabled at runtimecat /sys/kernel/mm/ksm/runAffected if The value is 1 (enabled) rather than 0 (disabled)
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Verify KSM daemon process statusps aux | grep -E 'ksmd|ksmtuned'Affected if A ksmd or ksmtuned process is running, indicating KSM is active
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Check kernel configuration for KSM supportgrep -i CONFIG_KSM /boot/config-$(uname -r) 2>/dev/null || cat /proc/config.gz 2>/dev/null | zgrep CONFIG_KSMAffected if CONFIG_KSM=y is set, meaning the kernel was built with KSM support
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Inspect KSM merge settings in sysfsls -la /sys/kernel/mm/ksm/Affected if The ksm directory exists and contains mergeable files, indicating KSM is operational
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Check for untrusted user access to KSM merge operationsls -la /sys/kernel/mm/ksm/ | grep -v rootAffected if Non-root users have write access to KSM merge control files, allowing them to trigger page deduplication
The system is affected if KSM is enabled (runtime=1) and untrusted local users can trigger or observe page merge operations.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataDisable Kernel Samepage Merging (KSM) if not required, or implement strict access controls on the deduplication feature to prevent untrusted local users from triggering page merge operations.
Fix this in Linux Kernel
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-3714 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-3714 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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